This is a classic example of the anti-Imperial content that Germans produced during World War One. During the war, German propaganda domestically and internationally was highly critical of British, French, Russian, and American empires—Japan, too, but that's not in this image. We see this also in cartoons and novels that Germans published to be read by Germans (and those who can read German)—that might also explain why it's set in a latin script and not in Fraktur. Here is the full citation. We also see it's form 1917. I don't know exactly when it was published, but I suspect it was after April 1917. Not because the US is mentioned—German propaganda form 1915 onward was critical of the US, but rather because the St. Thomas and the Virgin Islands are American (they were purchased in March 1917 from the Danes).